As described in International Patent Application Publication No. WO2005/024208 A1 and etc., a low output mode for allowing an engine to exert low output performance and a high output mode for allowing the engine to exert high output performance are set as engine output modes in work vehicles such as wheel loaders. Further, in the case of flatland travelling, for instance, light load acts on the engine, and therefore, the low output mode is selected for reducing fuel consumption. In the case of hill-climb travelling, by contrast, the high output mode is selected because a high output is required. Switching controls from the low output mode to the high output mode and vice versa are configured to be automatically executed depending on load and etc.